1. Field of the Invention
The present invention relates to a laser beam machining apparatus for machining materials by using a laser beam and, more particularly to a laser beam machining apparatus using a parallel link mechanism.
2. Description of Related Art
Laser beam machining apparatuses for performing machining such as cutting, boring, welding and surface treatment of a sheet-shaped material by using a laser beam have widely been employed as machining means suitable for production of a variety of products, each type being relatively small quantities, because of their advantages such as being capable of selecting machining shape freely. There are known two typical types of conventional laser beam machining apparatuses from the viewpoint of means for moving a machining head.
(1) A type of apparatus in which a machining head (laser head) is attached to an distal end of an industrial robot. In this type, the machining head is moved by the operation of the robot to thereby machine a sheet, a pipe and the like. Sometimes, a movement mechanism is additionally provided on the workpiece supporting side.
(2) A type of apparatus in which a gantry-type machine dedicated to laser beam machining is provided and a machining head is mounted at a movable end of an orthogonal movement mechanism. Sometimes, a movement mechanism is provided on the workpiece supporting side.
In the prior art of the above-described type (1), an operation range is wide and a degree of freedom of a wrist is large, so that this type of apparatus has an advantage of being suitable for machining of a three-dimensionally complex shape. However, most of robots have serially-operating constitution, so that it has a low rigidity as compared with a parallel-operating mechanism, and has a low absolute accuracy regarding the position of the machining head, which inhibits high-speed machining.
In the prior art of the above-described type (2), large-sized and heavy guides, frames, etc. are used for securing rigidity. Therefore, a high-power motor is necessary as a driving source, resulting in increase of manufacturing cost of the machine.
An object of the present invention is to provide a laser beam machining apparatus which has a higher rigidity than a laser beam machining apparatus of a conventional constitution, and therefore can easily perform high-speed driving of a machining head without decreasing the machining accuracy, and thereby efficiently perform highly accurate laser beam machining.
According to the present invention, there is provided a parallel link mechanism in which a stationary member and a movable member are connected to each other by a plurality of links, a machining head is supported on the movable member and the movable member is driven by the cooperative operation of the plurality of links to thereby move the machining head.
A feature of the laser beam machining apparatus of the present invention is that a movement mechanism for the machining head incorporates a parallel-operating driving system using the plurality of links for connecting the movable member to the stationary member. Thus, a substantial rigidity can be increased as compared with a laser beam machining apparatus of a conventional constitution using an X-Y orthogonal driving system. As a result, even if the machining head is moved at a high speed or at high acceleration, the machining accuracy is less prone to be decreased.
In a preferable mode, as means for changing a relative position of the machining head with respect to the workpiece, means for movably holding a workpiece is provided in addition to means for moving the machining head. Also, a supply line including a laser transmitting optical fiber, fluid supplying pipes and an electrical signal line is inserted through a hole formed inside a polygon formed by connecting link joint portions of the stationary member.
A hollow motor or a linear motor is preferably used as a driving source for the parallel link mechanism. In the case of hollow motor, it is preferable that an extensible axis of each link is provided through a hollow portion of the hollow motor, and the hollow motor is mounted on the stationary member using a gimbal joint.
In the case of linear motor, it is preferable that a coil and a cooling circuit are incorporated in a linear block, a magnet is incorporated in a rail and a gimbal joint is used for connecting the block with the stationary member.